As described herein, in certain aspects of the disclosure, hydrogen peroxide may be produced as a near-ideal gas phase, purified hydrogen peroxide gas (PHPG). In this form hydrogen peroxide behaves, in all respects, as a near-ideal gas and is not hydrated, or otherwise combined with water when produced.
The fundamental nature of a photocatalytic process is to create active intermediates in a chemical reaction by absorption of light. This occurs when a photon of the appropriate wavelength strikes the photocatalyst. The energy of the photon is imparted to a valence band electron, promoting the electron to the conduction band, thus leaving a “hole” in the valence band. In the absence of an adsorbed chemical species, the promoted electron will decay and recombine with the valence band hole. Recombination is prevented when the valence band hole captures an electron from an oxidizable species—preferentially molecular water—adsorbed to an active surface site on the photocatalyst. Concurrently, a reducible species adsorbed on the catalyst surface—preferentially molecular oxygen—may capture a conduction band electron.
Upon initiation of the photocatalytic process, or at the entrance point of a photocatalytic plasma reactor, the following reactions occur.